Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so safety is covered. The description adds genuine value beyond that by disclosing the field projection — only scheme, last four digits, and country are returned, with token, expiry, and address withheld — which sets expectations about what data the agent will and won't get. Pagination specifics (25 per page) are left to the schema.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

A single front-loaded sentence plus an endpoint reference, with no filler. The most decision-relevant detail, the restricted field projection, is placed before the endpoint.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description does important work by enumerating the returned fields and explicitly noting what is omitted. The only gap is that multi-page behavior and empty-result handling aren't described, but pagination mechanics are covered by the schema's page parameter.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, and both parameters (customer_token, page) are documented in the schema itself, including the cus_... token format and the 25-per-page pagination hint. The description adds nothing about parameters beyond that, so the baseline of 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a specific resource ('Cards stored for one customer') and scopes it precisely, plus the underlying endpoint GET /customers/{token}/cards. It is clearly distinguishable from siblings like pinpayments_list_customer_charges or pinpayments_list_customer_subscriptions, though the verb 'list' is implied rather than stated outright.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no explicit when-to-use or when-not-to-use guidance, and no routing to alternatives such as pinpayments_get_customer (for the customer itself). The reader must infer that this tool is for enumerating cards only, rather than for fetching a single card or the customer record.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.